Maharashtra State Board Class 10 Science Solutions Part 2 Chapter 2 Life Processes in Living Organisms Part – 1
b. At the end of glycolysis, ……………… molecules are obtained.
Answer:
At the end of glycolysis, pyruvate molecules are obtained.
c. Genetic recombination occurs in ………… phase of prophuse of meiosis-I.
Answer:
Genetic recombination occurs in pachytene phase of prophase of meiosis-I.
d. All chromosomes are arranged parallel to equatorial plane of cell in …………. phase of mitosis.
Answer:
All chromosomes are arranged parallel to equutorial plane of cell in metaphase phase of mitosis.
e. For formation of plasma membrane, phospholipid molecules are necessary.
Answer:
For formation of plasma membrane, …………… molecules are necessary.
f. Our muscle cells perform ……………… type of respiration during exercise.
Answer:
Our muscle cells perform anaerobic type of respiration during exercise.
b. Nutrients.
Answer:
Nutrients: The substances like carbohydrates, proteins, lipids, vitamins, minerals etc. which are components of the food are called nutrients.
c. Proteins.
Answer:
Proteins: Protein is a macromolecule which is formed by many amino acids which are joined by peptide bonds.
d. Cellular respiration.
Answer:
Cellular respiration: Oxidation of glucose and other food components which takes place inside the cell in presence or absence of oxygen, is known as cellular respiration.
e. Aerobic respiration.
Answer:
Aerobic respiration: Cellular respiration taking place in presence of oxygen is known as aerobic respiration.
f. Glycolysis.
Answer:
Glycolysis: The process occurring in the cell where a molecule of glucose is oxidized in step by step process forming two molecules of each of pyruvic acid, ATP, NADH2and water, is called glycolysis.
TCA cycle:
b. Mitosis and meiosis.
Answer:
Mitosis:
meiosis:
c. Aerobic and anaerobic respiration.
Answer:
Aerobic respiration:
Anaerobic respiration:
b. Fibres are one of the important nutrients. (Board’s Model Activity Sheet)
Answer:
c. Cell division is one of the important properties of cells and organisms.
Answer:
d. Sometimes, higher plants and animals too perform anaerobic respiration.
Answer:
e. Krebs cycle is also known as citric acid cycle.
Answer:
b. With the help of suitable diagrams, explain the mitosis in detail.
Answer:
(1) There are two stages of mitosis. These are
(a) Karyokinesis or nuclear division and
(b) Cytokinesis or cytoplasmic division. Karyokinesis takes place in further four phases, viz prophase, metaphase, anaphase and telophase.
(a) Karyokinesis:
(i) Prophase: During prophase, condensation of chromosomes starts. The thin and thread like chromosomes start thickening. They are seen with their pair of sister chromatids. In animal cells the centrioles are seen to duplicate and move to opposite poles of the cell. Nuclear membrane and nucleolus disappear.
(ii) Metaphase: Chromosomes complete their condensation and each one is seen with its sister chromatids. The chromosomes are seen in equatorial plane of the cell. The spindle fibres are formed from polar region, where centrioles are present, and they attach themselves to the centromere of each chromosome. Nuclear membrane now disappears completely.
(iii) Anaphase: The centromeres of the chromosomes now divide forming two daughter chromosomes. The spindle fibres pull apart the chromosomes from equatorial region to the opposite poles. Chromosomes moving to the poles appear like bunch of bananas. One set of chromosomes reach each pole by the end of the anaphase.
(iv) Telophase: Telophase is reverse of events that occurred in prophase. The thickened chromosomes decondense. They again assume the thin and thread like appearance. Nuclear membrane and nucleolus appear again. The spindle fibres are completely lost. The cell looks as if it has two nuclei in one cytoplasm.
(b) Cytokinesis: In animal cells a notch develops in the middle of the cell. This notch goes on deepening down and later the cytoplasm divides into two. In plant cells, cell plate formation takes place and then cytokinesis takes place.
c. With the help of suitable diagrams, explain the five stages of prophase-I of meiosis.
Answer:
Prophase-I: Prophase – I of meiosis is much longer phase of the meiosis.
It is subdivided into 5 substages, namely leptotene, zygotene, pachytene, diplotene, and diakinesis.
(1) Leptotene: Initially the chromosomes start condensation and they become compact during leptotene.
(2) Zygotene: In zygotene, homologous chromosomes start pairing. This pairing is called synapsis. The structure called synaptonemal complex develops to hold chromosomes in place during this pairing. Each chromosome’s chromatid arm divides and forms structure called bivalent or tetrad.
(3) Pachytene: During pachytene stage, crossing over of non-sister chromatids of homologous chromosomes takes place. Genetic recombination is produced due to such exchange. The homologous chromosomes still remain paired together at the sites of crossing over.
(4) Diplotene: During diplotene, synaptonemal complex dissolves and the homologous chromosomes of the bivalents separate except at the point of crossing over. Thus, it looks like X-shaped structures called the chiasmata.
(5) Diakinesis: The last phase of prophase is for termination of chiasmata. The spindle fibres originate, and the cross-over homologous chromosomes are now separated. The nucleQlus disappears, and the nuclear envelope breaks down.
d. How do all the life processes contribute to the growth and development of the body?
Answer:
e. Explain the Krebs cycle with reaction.
Answer:
(2) Oxidation of carbohydrates takes place during cellular respiration. Glucose is oxidized by three steps during aerobic respiration, viz. glycolysis, tricarboxylic acid cycle or Krebs cycle and electron transfer chain.
(3) From one molecule of glucose two molecules of each pyruvic acid, ATP, NADH2and water are formed during glycolysis. Pyruvic acid which is formed in this process is converted into Acetyl-Coenzyme-A along with release of two molecules each of NADH2and CO2.
(4) In the next step, i.e. in TCA cycle, molecules of Acetyl-Co-A enter the mitochondria and a cyclic chain of reactions take place. Acetyl part of Acetyl- Co-A is completely oxidized through this cyclical process. The molecules CO2, H2O, NADH2, FADH2are released in this process.
(5) In third step, i.e. in ETC reaction, NADH2and FADH2formed during first two steps are used for obtaining ATP molecules. 3 molecules of ATP are obtained from each NADH2molecule and 2 molecules of ATP from each FADH2.
(6) Thus, one molecule of glucose upon complete oxidation in presence of oxygen yields 38 molecules of ATP. This is how from carbohydrates, energy is obtained.
(7) If carbohydrates are insufficient in diet, then proteins or lipids are used for energy production. Fatty acids derived from fats and amino acids derived from proteins are converted into Acetyl- Co-A. Acetyl-Co-A once again can yield energy through TCA cycle.
Corrected diagram:
Project:
With the help of information collected from internet, prepare the slides of various stages of mitosis and observe under the compound microscope.
Can you recall? (Text Book Page No. 12)
Use your barain power:
Internet is my friend. (Text Book Page No. 17)
Collect information.
(a) What are symptoms of diseases like night blindness, rickets, beriberi, neuritis, pellagra, anaemia, scurvy?
Answer:
Disease | Symptoms |
Night blindness | Near sightedness, or blurred vision when looking at faraway objectsCataracts, or clouding of the eye’s lens.Inability to see in dark.Sometimes blindness. |
Rickets | Weak and soft bonesStunted growthIn severe cases, skeletal deformities. |
Beriberi | Decreased muscle function, particularly in the lower legs.Tingling or loss of feeling in the feet and hands.PainMental confusion, difficulty in speakingVomitingInvoluntary eye movement, paralysis. |
Neuritis | Numbness in hands and feetTingling sensation, sharp, jabbing, throbbing, freezing or burning pain.Extreme sensitivity to touch.Lack of coordination and falling. |
Pellagra | Delusions or mental confusion.Diarrhoea and nauseaInflammed mucous membrane.Scaly skin sores. |
Anaemia | Fatigue and loss of energyUnusually rapid heartbeat, particularly with exerciseShortness of breath and headache, particularly with exerciseDifficulty in concentratingDizziness, Pale skinLeg cramps, Insomnia |
Scurvy | Anaemia, debility, exhaustion,Spontaneous bleedingPain in the limbs, and especially the legs, swelling in some parts of the bodyUlceration of the gums and loss of teeth. |
(b) What do you mean by coenzymes?
Answer:
Co-enzyme is a non-protein compound that is necessary for the functioning of an enzyme. It is bound to the enzyme as a catalyst. This increases the rate of reaction. Co-enzymes always act along the enzymes. They cannot work independently. But the same molecule of coenzyme can be used again and again.
Many co-enzymes are vitamins or derived from vitamins. When vitamin intake is too low, then an organism also lacks the co-enzymes that catalyse reactions. Water-soluble vitamins, which include all B complex vitamins and vitamin C, lead to the production of co-enzymes. Two of the most important and widespread vitamin-derived coenzymes are Nicotinamide Adenine Dinucleotide (NAD) and co-enzyme A.
(c) Find the full forms of FAD, FMN, NAD, NADP.
Answer:
FAD | Flavin Adenine Dinucleotide |
FMN | Flavin Mono Nucleotide |
NAD | Nicotinamide Adenine Dinucleotide |
NADP | Nicotinamide Adenine Dinucleotide Phosphate |
(d) How much quantity of each vitamin is required every day?
Answer:
Vitamin | Daily requirement |
A | 700 and 900 μ grams |
B Complex | 100 mg/day for adults. |
C | 75 mg |
D | 5 μg |
E | 10 mg |
K | 80 μg |
Choose the correct alternative and write its alphabet against the sub-question number:
Write whether the following statements are true or false:
Match the columns:
Protein | Part of the body (July 2019) |
(1) Haemoglobin | (a) muscles |
(2) Ossein | (b) skin |
(c) bones | |
(d) blood |
Answer:
(1) Haemoglobin – blood
(2) Ossein – bones.
Protein | Part of the body |
(1) Keratin | (a) muscles |
(2) Myosin | (b) skin |
(c) bones | |
(d) blood |
Answer:
(1) Keratin – skin
(2) Myosin – muscles.
Find the odd one out:
Considering the relationship in the first pair, complete the second pair by using a word or group of words:
Write definitions:
Name the following:
Give scientific reasons:
Answer the following questions in detail:
(b) Name water soluble vitamins.
Answer:
Water soluble vitamins are B and C.
(c) Name fat soluble vitamins.
Answer:
Fat soluble vitamins are A, D, E and K.
(b) Give two examples of such living organisms.
Answer:
Yeast and bacteria.
(c) What are the two steps of anaerobic respiration?
Answer:
Glycolysis and fermentation are the two steps of anaerobic respiration.
Give explanations for the following statements:
Complete the paragraph by choosing the appropriate words given in the brackets:
Read the paragraph and answer the questions given below:
1. Dietary fibre — found mainly in fruits, vegetables, whole grains and legumes — is probably best known for its ability to prevent or relieve constipation. But foods containing fibre can provide other health benefits as well, such as helping to maintain a healthy weight and lowering your risk of diabetes, heart disease and some types of cancer. Dietary fibre, also known as roughage or bulk, includes the parts of plant foods your body can’t digest or absorb. Unlike other food components, such as fats, proteins or carbohydrates — which your body breaks down and absorbs — fibre isn’t digested by your body. Instead, it passes relatively intact through your stomach, small intestine and colon and out of your body.
Questions and Answers :
2. The substances formed by specific chemical bond between fatty acids and alcohol are called lipids. Digestion of lipids consumed by us is nothing but their conversion into fatty acids and alcohol. Fatty acids are absorbed and distributed everywhere within the body. From those fatty acids, different cells produce various substances necessary to themselves. Ex. the molecules called phospholipids which are essential for producing plasma membrane are formed from fatty acids. Besides, fatty acids are used for producing hormones like progesterone, estrogen, testosterone, aldosterone, etc. and the covering around the axons of nerve cells. We get 9 Kcal of energy per gram of lipids. Excess of lipids are stored in adipose connective tissue in the body.
Questions and Answers:
Diagram based questions:
(a) Which co-enzymes are shown in the diagram?
Answer:
The co-enzymes NADH2and FADH2are shown in the above diagram.
(b) Which chemical reaction takes place in the mitochondria? Which molecules are produced in this reaction?
Answer:
The chemical reaction that takes place in the mitochondria is called Electronic Transport Chain reaction. The molecules of H2O, carbon dioxide and energy in the form of ATP are produced in this reaction.
(b) What is the important difference between Telophase-I and Telophase-II of meiosis?
Answer:
In figure of Telophase-I the diploid chromosomes are seen in two daughter cells. In Telophase-II four daughter cells are seen with haploid chromosomes in them.
(c) Which figure shows phenomena of crossing over?
Answer:
The third figure of Prophase-I shows phenomena of crossing over.
Activity based questions:
Project:
Project 1.
Use of ICT: (Text Book Page No. 20)
Collect videos and photographs of different life processes in living organisms. Prepare a presentation and present it on the occasion of science exhibition.
Project 2.
Books are my friend: (Text Book Page No. 20)
Read different Encyclopaedias of technical terms in biology and anatomy and other reference books.